


teach me how

by celestialmuse



Category: Haikyuu!!
Genre: Age Difference, Alternate Universe - Babysitters, Baby!Omi, Babysitter!Atsumu, Babysitting, Fluff, Gen
Language: English
Status: Completed
Published: 2021-01-31
Updated: 2021-01-31
Packaged: 2021-03-17 06:47:31
Rating: General Audiences
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 1,456
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/29096004
Author URL: https://archiveofourown.org/users/celestialmuse/pseuds/celestialmuse
Summary: Atsumu is a babysitter and Kiyoomi is the dream baby to sit for. (No, really, I would only babysit for baby Omi and zero other people and Atsumu would agree).Just a lil snippet of their shenanigans
Relationships: Miya Atsumu & Sakusa Kiyoomi, Miya Atsumu/Sakusa Kiyoomi
Comments: 5
Kudos: 85





	teach me how

Kiyoomi was the cutest kid in the neighborhood and Atsumu considered himself lucky to babysit him. Plus, he was quiet, never cried, never threw a tantrum, ate his food—or just left it alone—and went to bed whenever Atsumu said it was time for bed. The dream babysitting job really. 

Kiyoomi was only seven years younger than Atsumu, but at twelve, having a five-year-old to babysit made Atsumu feel like an absolute authority figure, and having Kiyoomi actually listen to him only reinforced that feeling. 

At first, Kiyoomi didn’t even talk to Atsumu—he responded with curt little nods that would make his black curls bounce around when Atsumu spoke to him. After several nights of babysitting him—because Kiyoomi’s parents always worked late and his older sister had just moved out of their family home for university—Kiyoomi had said his first word to Atsumu when Atsumu had invited him to have dinner in the Kitchen. “Okay.” It was simple. One word. It made Atsumu’s heart nearly burst at the seams with the fondness and sense of accomplishment he felt when Kiyoomi finally, finally spoke to him. 

Kiyoomi was often alone at home and his parents didn’t want a nanny for him because he was a fairly independent child and a nanny would be a bad match for him. So they had decided to hire a babysitter who was only a few years older than Kiyoomi himself to keep him company after school until he went to bed at eight every weeknight. 

Atsumu was cheap labor and came with several high recommendations from friends and family, especially the Kitas’ and the Ojiros’, so he really couldn’t be that bad. Besides, the work was easy. Just keep Kiyoomi company, make sure he eats and drinks on time and help him get to bed by eight. Atsumu could even do his homework while he was babysitting. It was the perfect job for him.

Kiyoomi was a quiet child by nature. Atsumu had known him for a few weeks now and his favorite pastime seemed to be reading. He would quietly read in a corner on his little beanbag while Atsumu was often sprawled on the floor with his textbooks and homework sheets in front of him. 

Today had been a long day for Atsumu. He was worn out after his early morning volleyball practices and errands his mother had wanted him and Osamu to run after school. He had run to the Sakusas’ house to make it on time for his job. 

He knocked on the door while panting and little Kiyoomi opened the door for him, rubbing the sleep out of his eyes. He pouted at Atsumu. “You’re late, Tsumu-nii.”

Atsumu wanted to pinch his cheeks and put him in his pocket. That was the first time Kiyoomi had ever address him by name, much less with honorifics. 

“Ah, sorry Kiyoomi. Tsumu-nii had to run some errands. Sorry, I’m late,” he apologized sheepishly. “Did ya fall asleep?”

Kiyoomi nodded and opened the door wider to let Atsumu in. “Ma and Pa left a while ago.” 

“Ah, that so?” Atsumu asked as he dropped his bag in a corner and dug into it to grab his homework and some snacks. “Kiyoomi, do ya want some pudding?”

He watched Kiyoomi’s eyes light up as he speed-walked towards Atsumu with outstretched arms and Atsumu couldn’t help but grin and scoop him up into his arms. Kiyoomi squealed and wriggled and giggled in Atsumu’s arms as he spun them around a few times before carefully placing Kiyoomi back on the floor and ruffling his hair.

“Here ya go!” Atsumu said as he gave Kiyoomi a pudding cup and watched his eyes shine as he almost ran to the little table in the middle of the living room and sat down crosslegged before digging into it like the proper little boy he was. Atsumu badly wanted to squish his button nose but felt like that would be pushing it too far.

He spread his homework on the opposite side of the low table and dug into his own pudding cup as he worked through his math worksheet. Kiyoomi diligently picked up his own empty cup and Atsumu’s without asking and disposed of them while Atsumu continued to work.

He noticed Kiyoomi grab a book that had been lying face-down on the table and go settle into his little beanbag again. That book looked way too thick for a kid of his age but Atsumu knew Kiyoomi had a bigger brain than he did, so he didn’t bother questioning it. He powered through most of his homework and halfway through Japanese his eyes started to droop. He caught himself nodding off several times and tried to fight it, only to fail miserably. He noticed Kiyoomi watching him curiously, the book long forgotten on his lap.

“What’s up?” Atsumu asked, smiling at him.

“Is your homework that boring?” Kiyoomi asked bluntly. Atsumu couldn’t help but chuckle.

“Homework is always boring, Omi-kun,” Atsumu quipped, and watched little Kiyoomi wrinkle his nose at the shortened form of his name. “But nah, I’m just really tired today. Volleyball practice was extra hard today.” Atsumu punctuated his sentence with the motion of a receive, bouncing a phantom ball off his outstretched arms.

“You play volleyball?” Kiyoomi asked him, voice piqueing with curiosity.

Atsumu gasped. “Play? I play at the national level Omi-kun! I’m a setter!”

Kiyoomi scrunched his eyebrows together. “What’s a setter?”

Atsumu dramatically gasped again before explaining all the different positions in volleyball to Kiyoomi and they talked and talked about the sport until it was Kiyoomi’s bedtime.

“Tsumu-nii,” Kiyoomi called after he was tucked into bed by Atsumu. “Can you teach me how to play volleyball?”

Atsumu beamed at him. He couldn’t help but reach out and ruffle his curls with fondness. This kid was really starting to grow on him. “I’ll teach you tomorrow, okay?”

“Okay,” Kiyoomi agreed with a nod. “Good night!”

“Night, Omi!”

Atsumu kept his promise to a very eager Kiyoomi the next day. He came armed with three different volleyballs in three different sizes to make sure he had at least one that would fit Kiyoomi’s little hands. Atsumu set the net low in the Sakusas’ backyard and taught Kiyoomi the basics of receive-set-spike sequences and set to Kiyoomi again and again and again until he could no longer run for approach. 

He wobbled around on his little legs like a newborn fawn until he fell on the grass. Atsumu and Kiyoomi looked at each other in alarm until they both burst out laughing. 

“So, did ya like that Omi-kun?’ Atsumu asked, plopping down next to Kiyoomi and tossing him a bottle of water.

“I—I loved it, Tsumu-nii. Can we do that again?” Kiyoomi asked, with large puppy eyes and cheeks flushed from exertion. Atsumu really didn’t have it in him to say no to Kiyoomi.

“Absolutely. Did you like my tosses today?” Atsumu asked, ever the professional.

Kiyoomi nodded vigorously. “Tsumu-nii, I want to splay wing spiker so I can always hit Tsumu-nii’s tosses.”

If Atsumu blushed at that, he would have simply said he was feeling hot after a volleyball session. 

“Okay, then you have to become the best spiker Omi-kun, because Tsumu-nii doesn’t toss to scrubs okay? I want the best wing spikers.” Kiyoomi’s eyes shone with a wild sort of determination as he nodded slowly. 

“I will become the best wing spiker,” he declared solemnly. Atsumu didn’t have a single doubt that this kid would become one of the best, if not because of talent, because of sheer tenacity. He hadn’t let Atsumu stop tossing to him until he could finish spiking to his heart’s content.

“Hey Omi, ya want to learn from another wing spiker? I can ask Samu if he wants to come play with us?”

Atsumu had never seen Kiyoomi openly excited but his current expression was the closest he would ever get. Kiyoomi’s face stained with a fresh flush as he looked at Atsumu almost reverently and Atsumu didn’t need a verbal answer from him. 

“Alright, alright,” Atsumu laughed, helping Kiyoomi stand up. “I’ll ask Samu when he can join us. Let’s get cleaned up and get ya ready for bed, yeah?”

Kiyoomi headed to the shower at record speed and Atsumu was sure if the kid could fall asleep standing he would have. He helped Kiyoomi into his pajamas and carried him to bed. Atsumu gently tucked him under the covers and swept his bangs off his forehead. Kiyoomi had fallen asleep before he even hit the bed. 

“Night Omi,” Atsumu whispered as he turned off the lights in his room and gently shut the door after him. 

  
  


**Author's Note:**

> Thank you for reading! I really couldn't get the concept of Baby Omi out of my head and I feel like Atsumu has the best big bro vibes and he would literally die for a smol Omi.


End file.
